Finding air leaks

[stevec93]

Hi all my car idles badly and intermittently cuts out when stopping, there's no fault codes showing, so got no clues there. It's had new plugs and post cat lambda in last 6 month's as they were faulty but didn't cure the cutting out issue.

I've seen people say check for air leaks, what's the easiest way to do this? I've done boost leak checks on previous turbo cars by using a compressor, can I do the same on these? Or is there other ways

It's had a head gasket before so makes me think lower inlet gasket could be the issue, heard there awkward to get off, is this the same on a 172 cup with different aux belt set up?



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[imprezaworks]

Could be the upper inlet gasket, easy to do.

I bought mine from renault wolverhampton for less than a tenner delivered

 

[bloke]

quick liten around wiht a tube should show anything up then look at map sensor reading and injector duration at idle etc.

 

[DaveDreads]

An air leak in the intake system usually gives it a high idle of around 3k rpm.

 

[bloke]

An air leak in the intake system usually gives it a high idle of around 3k rpm.

small leak will give unsteady idle. normally up and down from idle to about 1,300rpm.

 

[DaveDreads]

True, but I've never heard of too much air making it cut out, that's usually a sensor or electrical issue.

 

[bloke]

me neither.

 

[White16valver]

Do they have idle speed control valves that could be cleaned or is it all done in the ECU?

 

[bloke]

phase 2 is done in throttle body. butterfly and body worth chercking/cleaning anyway.

 

[stevec93]

True, but I've never heard of too much air making it cut out, that's usually a sensor or electrical issue.

I was hoping if it was a sensor it would show a fault, and didn't want to go down trial and error route to find out what one is faulty since its not giving a fault code, so got told an air leak can cause these issues, it only stalls if you dip clutch quickly and revs drop low at same time, but seems to be getting more often now

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[Brigsy]

Have you scanned it with clip for fault codes? Is the cam timing correct ?

 

[Robbie Corbett]

Do you have a propane gas torch?

I've had success in the past by blowing propane (and possibly butane) around gasket joints to find leaks, when the idle increases/changes you've found your leak.

A simple stethoscope also works well, take some garden hose (fuel pipe works better, smaller), shove one end in your ear and move the other end around all gasket joints etc, often you can very clearly hear a vac leak this way, unless its massive!

However! in my experience, map sensor based engines are very tolerant to vac leaks, the two areas which cause big problems for map based cars are vac leaks around injectors or a badly split map sensor hose. As Bloke said above, manifold area leaks normally just mean a fluctuating idle rather than any terrible running as you would see with a MAF based system.

 

[Robbie Corbett]

Also changing the post cat lambda will have zero impact on running.

Change the pre cat lambda, or swap the pre and post if your post cat lambda is new (and a genuine part).

 

[Robbie Corbett]

Do you have any more information to share? Is the car new to you and has always had this issue? or has the problem developed over time?

If it is new to you and has always had the issue i would also suspect cam timing as mentioned above.

 

[stevec93]

Also changing the post cat lambda will have zero impact on running.

Change the pre cat lambda, or swap the pre and post if your post cat lambda is new (and a genuine part).

The lambda was changed due to being showing a fault code, and swapped them at time to see if it made a difference, but none

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[stevec93]

Do you have any more information to share? Is the car new to you and has always had this issue? or has the problem developed over time?

If it is new to you and has always had the issue i would also suspect cam timing as mentioned above.

It's always had a lumpy idle, more than my last 172, but the cutting out had been more recently, and when the car is cold it's very hesitant for a few mins. Timing belt is one of the things I thought off, but as it's got worse I thought maybe it's not

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[Trojanhawrs]

Never done it myself but heard you can spray WD40 around the gasket and should notice a change in revs if it finds a leak. Seems a nice easy solution unless anyone disagrees

 

[Robbie Corbett]

Get it plugged into CLIP and look for faults. This to me sounds like something has degraded over time rather than a timing change. Possibly coolant temp sensor, lambda, maybe an air leak or perhaps some combination of several things.

 

[bloke]

live data and look at map sensor reading, injector duration at idle and fuel trims.

 

[stevec93]

I went for trying map sensor first, I unplugged it and car ran better, didn't stall, and revs were alot more stable but it idled about 1100 unplugged, so fitted a new geniune Renault one, car pulls so much better than it did before, it's not hesitating, and hasn't stalled yet, but revs are still a bit lumpy, it sometimes feels like it's about to stall but then saves it

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[bloke]

ouch, map sensor ain't cheap!!

 

[stevec93]

ouch, map sensor ain't cheap!!

At least it solved something though, car runs alot better, just not perfect yet.

1 other thing I've noticed is when using mobile app torque (not expecting this to be reliable) with the car off it's showing 220 rpm on the graph, could this be anything or just the app? With the car running it shows correct rpm

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[bloke]

They don't read zero, can't remember what they do read but that sounds familiar.